Protein synthesis is the major biosynthetic activity of growing cells. The complete biosynthetic process in Escherichia coli is complex and requires RNA polymerase, transcription factors for initiation and termination, ribosomes, translation factors for initiation, elongation and release of peptides and amino acylated tRNA's. The fraction of the cellular metabolic activity devoted to the production of these components is substantial and dependent upon the growth rate of the cells. Knowledge of the function and regulation of transcription and translation components is clearly essential for understanding cell growth. This proposal requests support for in vivo physiological studies dealing with control of the expression of genes coding for these components and dealing with the interactions and relationships between these components during the processes of transcription and translation. These physiological studies will employ double isotope labeling, purification of proteins by antibody precipitation and/or gel electrophoresis and assay of RNAs by specific and sensitive RNA-DNA hybridization techniques. These physiological experiments will be complimentary to the substantial genetic and in vitro biochemical efforts being carried on in many other laboratories. The proposed studies are relevant and of fundamental importance in elucidating the roles of individual components in protein synthesis and, more importantly, in identifying factors, elements or control systems which determine the patterns of RNA transcription and regulate and maintain balanced production of cellular components during exponential phase growth. Many of the findings will be applicable to eucaryotic as well as procaryotic systems.